Kei often gets involved in fights, despite of him being weak and always end up losing… One day, while helping a friend to bring some textbooks to an old building of his school, he and his childhood friend, Tomoe, are attacked by a monster. In order to save his friend, Kei will choose to become a Grave Protector!

* Cerberus in ancient Greek mythology was a three headed hell hound with a snake tail that guarded the gates of the Underworld preventing those who have crossed the river Styx from ever escaping.

from Easy Going Scans

The series Cerberus has been licensed, it is not available in Manga Fox.